In Akron, Ohio, situated amid industrial buildings and auto service centers, is a small oasis of polished steel and nonslip scaffolding. The proprietors of this new facility hope it’s the future of the plastics industry.
The facility, a pyrolysis plant run by Alterra, breaks down plastic waste into a crude oil–like mixture that can be fed into petrochemical plants and transformed back into new plastics.
The plant can process about 60 metric tons (t) of plastics a day. It was the largest operational plastics pyrolysis plant in the US until recently, when it was edged out by a larger facility that ExxonMobil started up in Houston. Many more pyrolysis plants, including ones using Alterra’s technology, are on drawing boards for sites around the world.
Journalists visited the Alterra plant in November during a trip organized by the American Chemistry Council, a trade group keen on promoting plastics recycling by pyrolysis, depolymerization, and other emerging techniques the industry calls advanced recycling. Industry aims for such technologies to take hold and thereby improve the image of the plastics industry.
Jeremy DeBenedictis, Alterra’s president, told the group in a conference room at the plant’s offices that he has bold aspirations. “It’s a small amount of material right now,” he acknowledged. Polymerization plants that make new plastics are orders of magnitude bigger. But DeBenedictis quickly shifted to an optimistic gear, noting that a decade ago Tesla was only making a few thousand cars in a year. “Do you know how many they’ll make next year? Two million. New technologies will get there when they are embraced by the public and embraced by industry.”
DeBenedictis joined Alterra around the time Tesla was just starting to build cars. Back in 2011, he was a manager at General Electric, running a business making targets for computed tomography scanners and X-ray machines. He wanted to try running a start-up, so he joined Alterra, then known as Vadxx Energy. At the time, it was a three-employee outfit with a tabletop reactor, which literally sat in a garage, that could process about 2 kg of plastic waste per hour.
Dozens of small companies like Alterra around the world are developing plastics pyrolysis processes. The facilities they are building are meant to solve a dilemma. Conventional mechanical recycling, in which plastics are collected, sorted, washed, and melted down for reuse, has its limitations. Notably, the streams of waste plastics must be relatively homogeneous.
Thus, the vast majority of plastics recycled in the US are high-density polyethylene and polyethylene terephthalate bottles and containers, which are easy to sort. It’s no wonder that the overall plastics recycling rate in the US has struggled to break 9%; most of the rest goes to a landfill.
Compared with mechanical recycling facilities, pyrolysis plants can take in a wider variety of plastics, including film and flexible packaging. They are also more robust when it comes to handling the mixing of plastics that occurs when different materials are used in packaging or combined in the recycling stream. The plastics all break down together in the same kiln.
Still, the preferred feedstocks for pyrolysis plants are polyolefins, such as polyethylene and polypropylene, and polystyrene. Plant operators try to eliminate, sometimes by physically sorting them out, plastics containing chlorine, oxygen, and nitrogen—such as polyvinyl chloride (PVC), polyethylene terephthalate, and nylon—to the extent they can to minimize non-hydrocarbon impurities in their final product.
Alterra’s forebear, Vadxx, was founded by inventor William Ullom in 2009 when he purchased the rights to University of Wyoming patents. They were a starting point. Working in that garage, Ullom and other Vadxx engineers made changes to the process until they had something all their own. Alterra now has three patents and four patent applications.
DeBenedictis said the engineers set out to make the operation continuous. Most other pyrolysis processes under development are centered on batch reactors, which are less efficient. Alterra has also kept the process simple by shunning the use of catalysts to assist the pyrolysis reaction.
To demonstrate how omnivorous the Akron plant is, DeBenedictis asked the reporters to bring plastic debris to throw in the pyrolysis reactor. One reporter gathered detritus from his hotel room: the plastic bags that cover the cups, a plastic cup itself, the wrapping for the soap.
Alterra has grown out of the garage. The pyrolysis facility, which started up in 2020, employs 32 people and has all the trappings of a traditional chemical plant, with interconnected pipes, fittings, and vessels. Visitors must don hard hats, safety glasses, steel-toed shoe covers, and fire-resistant jumpsuits before they are permitted on the factory floor.
The office area opens up onto a concrete bunker that can store 500 t of waste plastic. DeBenedictis said the company pays a “small amount” for its feedstock, 50–75% of which comes from facilities around the Midwest that process what residents throw in their recycling bins. About 80% of the material arrives shredded and densified by Ravago, a plastics distributor and recycler that invested in Alterra.
The balance is postindustrial residue, such as cuttings from diaper manufacturing or bits of pipe made from cross-linked polyethylene. These kinds of materials, said Kevin Dressler, Alterra’s director of licensing, cannot be mechanically recycled and would otherwise go to a landfill.
In the bunker, the plastics, predominantly polyethylene and polypropylene, are heaped in gray piles randomly sprinkled with colors. Fragments of packaging labels can be seen in the shredded and compacted bits of plastic.
A front-end loader drops the shreds into a hopper, and a conveyor belt carries them to an extruder. The plastic comes out of the extruder with the consistency of saltwater taffy and is sent by pipe to the reactor. The purpose of the extrusion step is to heat the plastic and give it uniform density so it can transfer heat predictably in the pyrolysis reactor.
At this stage, the plastic is mixed with calcium oxide, which scavenges for chlorine from errant PVC. Chlorine can corrode and damage downstream customers’ chemical production equipment if it remains in the pyrolysis oil. DeBenedictis said the calcium oxide reacts with chlorine to form calcium chloride, removing about 80% of the halogen. Customers handle the rest by chemically upgrading the pyrolysis oil themselves.
The pyrolysis reactor is a cylinder about 3 m in diameter and 20 m long. It rotates slowly to mix the contents and is angled downward to allow gravity to keep the fluids flowing. Inside, plastics are heated to about 400–550 °C in the absence of oxygen. This energy breaks down the long polymer chains into smaller hydrocarbons ranging from gaseous 3-carbon propane up through waxes of 30 carbons or more.
The longer-chain hydrocarbon liquids, which compose 70–80% of the plant’s output, are run through a multistage condenser system and then recombined into a final product that is solid at room temperature. One or two trucks, each capable of carrying 22,000 L of the material, depart every day from Akron, headed south to petrochemical customers on the US Gulf Coast.
The rest of the hydrocarbon output is noncondensable gases. The gases supplement the natural gas used to fire the kiln. Another 10% of the total material that exits the reactor is solid char, a mixture of carbon and inorganics such as calcium chloride. This flows into large sacks that hang near the kiln and can be used in asphalt, DeBenedictis said.
Alterra’s long-term goal is to license the technology to third parties, not build more plants itself, as most other pyrolysis firms are doing. The Akron plant is meant to “demonstrate the technology at a commercial scale to potential companies who will license it from us and build their own plants,” DeBenedictis said.
When asked whether the plant is turning a profit, he said it “absolutely can” be profitable, though he noted that the long distance between the facility and its customers poses a challenge.
The technology has already generated interest outside Akron. Ravago and the Finnish refiner Neste, also an Alterra investor, are planning a plant in Vlissingen, the Netherlands, capable of processing 55,000 t of waste annually. Abundia Global Impact plans to build a plant in the UK capable of processing 40,000 t per year of waste.
Alterra is also working on multiple projects on the US Gulf Coast with “major petrochemical players,” DeBenedictis said, and announcements of new initiatives should come within the next few quarters.
But will pyrolysis actually take off? Marco J. Castaldi, a chemical engineering professor at the City College of New York, has been monitoring plastics pyrolysis for 20 years. The time, he says, may finally be right.
Castaldi says the technology itself hasn’t been the hurdle for acceptance. “This stuff is well known,” he says. “What’s changed is, honestly, the recognition that something must be done with the plastics that cannot be recycled.”
The problem is enormous. For instance, only half of the plastics thrown in blue bins in New York City actually get recycled, Castaldi says. What remains is a stream of residues that might lend itself to pyrolysis. Sending this waste to a landfill is irrational, Castaldi notes.
And nowadays, major oil and petrochemical companies are more interested than they used to be in making products derived from recycled material, Castaldi says. “They are now seriously engaging in finding streams of oil that they can process or refine to products other than fuels,” he says.
The chemical industry may have embraced pyrolysis, but if the technology is to solve its problems, the process will need to work, and work economically. The facility in Akron, may be a beginning.